Molecules in Motion

Pressure
Pressure is the force acting per unit area. As forces are applied to ever larger areas there strenght is reduced, as a well as increased strengths from forces being applied to ever smaller areas. Drawing pin being a good example of pressure as its tiny surface along with a large force. P=F/A. The unit of pressure is Pascal (Pa). 1 Pascal is the same as 1 newton acting over a square meter.

Kinetic theory of gasses and pressure
Pressure can be interpreted as the movement of molecules in a confined space. Assuming that:
 * Molecules are in constant rapid motion
 * Each molecule volume is negliable compared to whole system
 * At any instant many molecules are moving in one direction as well as all other directions
 * Molecules undergo perfectly elastic collisions with container walls
 * Only considering kinetic energy of molecules
 * Each molecule produces a force on the wall container
 * Uniform pressure throughout the gas as well as no gravitational effects.

Where p is the gas pressure, V is the volume of the gas. N is the number of molecules in the gas M is the mass of a single molecule and is  c² is the Mean square velocity of the molecules.

Changing the pressure

Increasing the number of molecules of gas in the container can be seen from the equation to show an increase in the pressure of the system, as collisions would happen between the container walls more frequently. Double the number of molecules would double the rate of collisions with the walls and double the pressure. A smaller volume for the same amount of gas to be in would also increase the pressure. NM/V is the gas density. The total mass of the gass over the volume it is in. The higher the gas density the higher the pressure.